Australians have overwhelmingly voted in favour of legalising same-sex marriage in a historic poll.

Australians have overwhelmingly voted in favour of legalising same-sex marriage in a historic poll.

The non-binding postal vote showed 61.6% of people favour allowing same-sex couples to wed, the Australian Bureau of Statistics said.

The non-binding postal vote showed 61.6% of people favour allowing same-sex couples to wed, the Australian Bureau of Statistics said.

Jubilant supporters have been celebrating in public spaces, waving rainbow flags and singing and dancing.

Jubilant supporters have been celebrating in public spaces, waving rainbow flags and singing and dancing.

The issue only went to a voluntary postal vote after a long and bitter debate about changing the law.

The issue only went to a voluntary postal vote after a long and bitter debate about changing the law.

Prime Minister Malcolm Turnbull said his government would now aim to pass legislation in parliament by Christmas.

Prime Minister Malcolm Turnbull said his government would now aim to pass legislation in parliament by Christmas.

"[Australians] have spoken in their millions and they have voted overwhelmingly yes for marriage equality," Mr Turnbull said after the result was announced.

"[Australians] have spoken in their millions and they have voted overwhelmingly yes for marriage equality," Mr Turnbull said after the result was announced.

"They voted yes for fairness, yes for commitment, yes for love. And now it is up to us here in the parliament of Australia to get on with it."

"They voted yes for fairness, yes for commitment, yes for love."

More than 12.7 million people - about 79.5% of eligible voters - took part in the eight-week postal survey

The result on Wednesday brings an end to what was at times a heated campaign. The vote itself had been criticised by same-sex marriage supporters, many of whom said it was unnecessary when parliament could debate the issue directly.

The result on Wednesday brings an end to what was at times a heated campaign. The vote itself had been criticised by same-sex marriage supporters, many of whom said it was unnecessary when parliament could debate the issue directly.

How did the vote unfold?

How did the vote unfold?

The survey was voluntary, unlike Australia's compulsory elections.

The survey was voluntary, unlike Australia's compulsory elections.

Voters were asked to mail back a Yes or No response to the question: "Should the marriage law should be changed to allow same-sex couples to marry?"

More than 12.7 million people - about 79.5% of eligible voters - took part in the eight-week poll, which asked one question: "Should the marriage law should be changed to allow same-sex couples to marry?"

The Yes campaign argued that it was a debate about equality. The No campaign had put the focus on the definition of family, raising concerns about how issues like gender will be taught in schools.

The Yes campaign argued that it was a debate about equality. The No campaign put the focus on the definition of family, raising concerns about how issues like gender will be taught in schools.

What were the results?

What were the results?

Australia's chief statistician David Kalisch said about 7.8 million people voted in support of same-sex marriage, with approximately 4.9 million against it.

Australia's chief statistician David Kalisch said about 7.8 million people voted in support of same-sex marriage, with approximately 4.9 million against it.

He said participation was higher than 70% in 146 of Australia's 150 electorates. All but 17 electorates supported changing the law.

He said participation was higher than 70% in 146 of Australia's 150 electorates. All but 17 electorates supported changing the law.

"This is outstanding for a voluntary survey and well above other voluntary surveys conducted around the world," Mr Kalisch said.

"This is outstanding for a voluntary survey and well above other voluntary surveys conducted around the world," Mr Kalisch said.

"It shows how important this issue is to many Australians."

"It shows how important this issue is to many Australians."

What happens next?

What happens next?

Mr Turnbull, a strong same-sex marriage supporter, is facing debate within his government over what the parliamentary bill should include.

Mr Turnbull, a strong same-sex marriage supporter, is facing debate within his government over what the parliamentary bill should include.

Some conservative MPs are pushing for the bill to include exemptions that would allow businesses opposed to same-sex marriage to refuse goods and services for weddings.

Some conservative MPs want it to contain exemptions that would allow businesses opposed to same-sex marriage to refuse goods and services for weddings.

But matters are complicated: two government politicians have proposed introducing separate bills to parliament to legislate same-sex marriage.

But matters are complicated: two government politicians have proposed introducing separate bills to parliament to legislate same-sex marriage.

One bill, by Senator Dean Smith, has broad support from opposition parties and many members of the government, including Mr Turnbull.

One bill, by Senator Dean Smith, has broad support from opposition parties and many members of the government, including Mr Turnbull.

An alternative bill, suggested by Senator Paterson, has drawn support from more conservative MPs who say it provides stronger religious protections.

An alternative bill, suggested by Senator James Paterson, has drawn support from more conservative MPs who say it provides stronger religious protections.

What has been the reaction?

What has been the reaction?

"This is an amazing outcome and we should all be very proud of this amazing country," Qantas chief executive Alan Joyce, a prominent same-sex marriage supporter, told a jubilant crowd in Sydney.

"This is an amazing outcome and we should all be very proud of this amazing country," Qantas chief executive Alan Joyce, a prominent same-sex marriage supporter, told a jubilant crowd in Sydney.

Former Prime Minister Tony Abbott, a high-profile same-sex marriage opponent, said the parliament should "respect the result".

Former Prime Minister Tony Abbott, a high-profile same-sex marriage opponent, said the parliament should "respect the result".

"I always said this was an issue where the Australian people wanted their say and today's result demonstrates that seeking their views was the right thing to do," he wrote on Facebook.

He wrote on Facebook that he would support a bill that provided "freedom of conscience for all, not just the churches".

He said he supported a bill that provided "freedom of conscience for all, not just the churches".

Another prominent No campaigner, Lyle Shelton, said: "We will now do what we can to guard against restrictions on freedom of speech and freedom of religion, to defend parents' rights, and to protect Australian kids from being exposed to radical LGBTIQ sex and gender education in the classrooms."

Another prominent No campaigner, Lyle Shelton, said: "We will now do what we can to guard against restrictions on freedom of speech and freedom of religion, to defend parents' rights, and to protect Australian kids from being exposed to radical LGBTIQ sex and gender education in the classrooms."

Why was the vote controversial?

Why was the vote controversial?

The postal survey followed two failed attempts by the government to hold a compulsory national vote that was twice voted down by the Senate.

The postal survey followed two failed attempts by the government to hold a compulsory national vote that was twice voted down by the Senate.

Senators who opposed the compulsory vote did not necessarily oppose legalisation, but said the vote would be costly and fuel hate campaigns. They argued the matter should be put to a parliamentary vote.

Senators who opposed the compulsory vote did not necessarily oppose legalisation, but said the vote would be costly and fuel hate campaigns. They argued the matter should be put to a parliamentary vote.

Many supporters of same-sex marriage levelled the same criticism at the voluntary vote, which did not require legislative approval.

Many same-sex marriage advocates levelled the same criticism at the voluntary vote, which did not require legislative approval.

During the campaign, each side has accused the other of bullying and misleading discussion, while the debate was even linked to violent incidents.

During the campaign, each side has accused the other of bullying and misleading discussion, while the debate was even linked to violent incidents.